Oncolytic vaccinia virus demonstrates antiangiogenic effects mediated by targeting of VEGF

摘要

Oncolytic vaccinia virus has been shown to induce a profound, rapid and tumor-specific vascular collapse in both preclinical models and clinical studies; however, a complete examination of the kinetics and levels of collapse and revascularization has not been described previously. Contrast-enhanced ultrasound was used to follow tumor perfusion levels in mouse tumor models at times after vaccinia therapy. It was observed that revascularization after viral therapy was dramatically delayed and did not occur until after viral clearance. This indicated that oncolytic vaccinia may possess a previously undescribed antiangiogenic potential that might synergize with the reported anti-vascular effects. Despite a rapid loss of perfusion and widespread hypoxia within the tumor, it was observed that VEGF levels in the tumor were suppressed throughout the period of active viral infection. Although tumor vasculature could eventually reform after the viral therapy was cleared in mouse models, anti-tumor effects could be significantly enhanced through additional combination with anti-VEGF therapies. This was initially examined using a gene therapy approach (Ad-Flk1-Fc) to target VEGF directly, demonstrating that the timing of application of the antiangiogenic therapy was critical. However, it is also known that oncolytic vaccinia sensitizes tumors to tyrosine kinase inhibitors (TKI) in the clinic through an unknown mechanism. It is possible this phenomenon may be mediated through the antiangiogenic effects of the TKIs. This was modeled in mouse tumors using sunitinib in combination with oncolytic vaccinia. It was observed that prevention of angiogenesis mediated by oncolytic vaccinia can be utilized to enhance the TKI therapy. What's new? The induction of vascular collapse within a tumor is a promising therapeutic strategy, one that may be achieved with oncolytic vaccinia virus. In this study, oncolytic vaccinia virus was found to dramatically delay tumor revascularization following vascular collapse. The period of viral infection was further associated with VEGF suppression. In mice, the administration of anti-VEGF therapies significantly enhanced the antitumor effects of vaccinia therapy, even after the virus was cleared. The findings shed light on the importance of timing in combination therapies and on the reported benefits of combined oncolytic vaccinia virotherapy and tyrosine kinase inhibition.